Old As;e and Death. 29 



*& 



excitability of the system; as during any diminution of the usual 

 quantity of stimulus, an accumulation of sensorial power is produced; 

 and in consequence the excitability, which was lessened by the action 

 of habitual stimulus, becomes restored. Thus those, who are uni- 

 formly habituated to much artificial heat, as in warm parlours in the 

 winter months, lose their irritability in some degree, and become 

 feeble like hot-house plants; but by frequently going for a time into 

 the cold air, the sensorial power of irritability is accumulated and 

 they become stronger. 



Whence it may be deduced, that the variations of the cold and 

 heat of this climate contribute to strengthen its inhabitants, who are 

 more active and vigorous, and live longer, than those of either much 

 warmer or much colder latitudes. 



This accumulation of sensorial power from diminution of stimulus 

 any one may observe, who in severe weather may sit by the fire-side 

 till he is chill and uneasy with the sensation of cold; but if he walks 

 into the frosty air for a few minutes, an accumulation of sensorial 

 power is produced by diminution of the stimulus of heat, and on his 

 returning into the room where he was chill before, his whole skin 

 will now glow with warmth. 



Hence it may be concluded, that the variations of the quantity of 

 stimuli within certain limits contribute to our health; and that those 

 houses which are kept too uniformly warm, are less wholesome than 

 where the inhabitants are occasionally exposed to cold air in passing 

 from one room to another. 



Nevertheless to those weak habits with pale skins and large pupils 

 of the eyes, whose degree of irritability is less than health requires, 

 as in scrofulous, hysterical, and some consumptive constitutions, a 

 climate warmer than our own may be of service, as a* greater stimulus 

 of heat may be wanted to excite their less irritability. And also a 

 more uniform quantity of heat may be serviceable to consumptive 

 patients than is met with in this country, as the lungs cannot be 

 clothed like the external skin, and are therefore subject to greater 

 extremes of heat and cold in passing in winter from a warm room into 

 the frosty air. 



4. It should nevertheless be observed, that there is one kind of 



